As part of the program project grant, calibration, estimates of stability, determination of effect on tissues, physiology, and mutagenicity and affect on isolated cells of various EPR substrate oxygen sensitive probes will be carried out. The substrates will include LiPc, fusinite, chars, india ink, encapsulated nitroxides and plastic encapsulated high spin density carbon particulates. These will be used to determine pO2 in various animal organs and will allow the measurement of the effect of anesthesia.